This invention relates to an apparatus for the selection of lighting fixtures. In particular, it is an improved means of determining the number of fixtures necessary to provide a predetermined level of illumination in a given space.
The selection of lighting fixtures for use in a given space involves certain calculations, certain assumptions, and the application of tabulated information. The dimensions of a room to be illuminated and their ratio to each other affect the selection of lighting fixtures. The function to be performed in a given space normally determines the required lighting level in footcandles. Tabulations exist of recommended illumination values in footcandles for different activities. The amount of light produced by various combinations of light sources and reflectors can be measured and tabulated. These figures can be modified by taking into account anticipated decreases in light output from such fixtures as a function of time and as a function of the average cleanliness of the fixtures.
The process of selecting a recommended pattern of lights to meet various specifications becomes one of calculating the number of lights required and their spacing from each other based upon an input of the parameters described above. The purchase cost of a lighting system for a space is a function of the type of unit that is used and the number of units required. Selection of the lighting units to be used for particular installation thus requires a number of calculations and the use of various tabulated descriptive factors. For major new construction, the decision as to which lighting units to select is often made by entering parameters in a main-frame computer that is programmed to calculate and print out the results of selecting various options. A manufacturer of lighting elements, for example, can typically devote time from a main-frame computer to carry out such calculations for customers.
In contrast, a dealer, distributor or lighting contractor may not have a main-frame computer available to be programmed for the solution of lighting problems, or may not have enough lighting problems to solve to make it worth the effort of programming such a computer. The dealer or distributor is therefore forced either to resort to repeated calculations by pencil and paper to reach approximate solutions, or to refer such questions to the manufacturer for solution. The first of these approaches is relatively expensive and inefficient, while the second approach takes time to get back answers. It would be useful to have a method and means of determining the solution to lighting problems at or near a job site with a relatively inexpensive apparatus.